Nonadiabatic Effects in Photodissociation of Small Molecules

化学学部的理论与计算化学项目支持托莱多大学郭教授对化学反应中的曲线交叉事件进行的全面研究。郭教授正在进行小分子光解的非绝热跃迁动力学的研究，包括气相中碘化烷基光解动力学的新的三维量子力学计算。郭教授的新方法通过量子波包方法处理解离自由度，同时用经典轨迹表征环境运动。量子子系统和经典子系统通过Ehrenfest格式耦合，使波包和轨迹能够自洽地传播。大多数化学反应都可以充分理解为反应物分子和生成物分子处于基电子态。然而，有许多重要的反应，包括大多数由紫外线辐射引发的过程，其反应过程涉及基态和激发态之间的相互作用。一种新的理论方法正在测试中，它将允许预测这些过程的可能性，从而有助于理解由光引发的过程的机制。

The Theoretical and Computational Chemistry Program in the Chemistry Division has supported a comprehensive investigation of curve-crossing events in chemical reactions being carried out by Professor Guo at the University of Toledo. Professor Guo is conducting a study of non-adiabatic transition dynamics in the photodissociation of small molecules, including new three-dimensional quantum mechanical calculations of the photodissociation dynamics of alkyl iodides in the gas phase. Professor Guo's new approach treats the dissociation degree of freedom by a quantum wavepacket method while characterizing environment motions by classical trajectories. The quantum and classical subsystems are coupled via the Ehrenfest scheme so that the wavepacket and the trajectory can be propagated self-consistently. %%% Most chemical reactions can be adequately understood as involving reactant and product molecules in their ground electronic states. However, there are many important reactions, including most processes that are initiated by ultraviolet radiation, for which the reaction process involves interaction between the ground and excited electronic states. A new theoretical method is being tested that should permit prediction of the probability of such processes and thereby contribute to the understanding of the mechanisms of processes initiated by light.